Move |PlatformFont::GetStringWidth()| implementation up into font.cc directly.

ui/gfx/platform_font_win.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_PLATFORM_FONT_WIN_H_
 #define UI_GFX_PLATFORM_FONT_WIN_H_
 #pragma once
 
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
@@ skipping 28 matching lines @@
   // performed other than clamping to a minimum font height if
   // |get_minimum_font_size_callback| is specified.
   typedef void (*AdjustFontCallback)(LOGFONT* lf);
   static AdjustFontCallback adjust_font_callback;
 
   // Overridden from PlatformFont:
   virtual Font DeriveFont(int size_delta, int style) const OVERRIDE;
   virtual int GetHeight() const OVERRIDE;
   virtual int GetBaseline() const OVERRIDE;
   virtual int GetAverageCharacterWidth() const OVERRIDE;
-  virtual int GetStringWidth(const string16& text) const OVERRIDE;
   virtual int GetExpectedTextWidth(int length) const OVERRIDE;
   virtual int GetStyle() const OVERRIDE;
   virtual std::string GetFontName() const OVERRIDE;
   virtual int GetFontSize() const OVERRIDE;
   virtual NativeFont GetNativeFont() const OVERRIDE;
 
  private:
   virtual ~PlatformFontWin() {}
 
   // Chrome text drawing bottoms out in the Windows GDI functions that take an
@@ skipping 63 matching lines @@
   static HFontRef* base_font_ref_;
 
   // Indirect reference to the HFontRef, which references the underlying HFONT.
   scoped_refptr<HFontRef> font_ref_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_PLATFORM_FONT_WIN_H_